When inorganic porous materials for architectural or civil engineering are used in outdoor structures, they are exposed to rain and deteriorated by absorbed water, cause cracks due to freezing at low temperatures or damage by salt at seasides, and deterioration in appearance due to adhesion of fungi and algae. Therefore, measures to extend life spans of the structures are desired.
Examples of the inorganic porous materials include concrete, lightweight concrete, autoclaved lightweight aerated concrete (ALC), mortar, cement plates, plaster boards, calcium silicate plates, bricks, tiles and stones. In order to prevent deterioration of these porous materials, a water absorption-preventing agent is applied on and penetrates through a surface of the porous material to make the surface hydrophobic and prevent water and salts from penetrating through the surface of porous materials. Silicone compositions are known as a water absorption-preventing agent.
As the water absorption-preventing silicone agent, a solvent-borne water absorption-preventing agent comprising alkylalkoxysilane diluted with an organic solvent is known. However, a concentration of the alkylalkoxysilane and the viscosity are low in this water absorption-preventing agent. Therefore, a sufficient amount of the alkylalkoxysilane does not penetrate through a surface of a substrate by one-time application, so that a hydrophobic layer with a sufficient thickness is not formed on the surface of the substrate. Further, after applying the solvent-borne water absorption-preventing agent, VOCs, i.e. volatility organic compounds, evaporate from the organic solvent to deteriorate working environment and environmental problems. Therefore, a non-solvent type water absorption-preventing agent is desired in recent years.
Japanese Patent Application Laid-Open Nos. Sho62-197369, Hei-4-111979, Hei-6-313167, Hei-9-208938 and 2004-315631 describe that aqueous emulsion compositions comprising an alkylalkoxysilane, a surfactant or emulsifier and water are used as a water absorption-preventing agent. However, the surfactant remains on a surface of a substrate after applying the aqueous emulsion composition, so that the surface is not made sufficiently hydrophobic. Therefore, there are problems at the time of rain such that parts of the surface of the substrate have wet color to deteriorate the appearance and sufficient water repellency cannot be obtained.
Further, there is a problem such that the aqueous emulsion flows down when the aqueous emulsion is applied thickly on a surface of a substrate or applied on a vertical surface. Japanese Patent Application Laid-Open No. Hei-10-81824 describes that an aqueous cream, that is, water-containing paste composition, comprising an alkylalkoxysilane, an emulsifier and water is used as a water absorption-preventing agent. This water absorption-preventing agent is cream, so that it can be applied thickly on a surface of a substrate. However, in a short time after applying the agent, the emulsion state breaks and the alkylalkoxysilane having a low viscosity separates. Therefore, when the composition is applied on an inclined or vertical surface or an inverted surface of a substrate, dripping occurs, so that an effective component, alkylalkoxysilane, flows away and does not penetrate sufficiently through the surface.
Japanese Patent Application Laid-Open No. 2009-155641 describes a water absorption-preventing agent prepared by dispersing an alkylalkoxysilane and cyclodextrin in water. This water absorption-preventing agent leaves the cyclodextrin, which is a water soluble polymer, on a surface of a substrate, after applied and, therefore, the appearance of the substrate was deteriorated and sufficient water repellency cannot be obtained.
Japanese Patent Application Laid-Open No. 2009-35704 describes a water absorption-preventing agent comprising an alkylalkoxysilane and silica. The composition leaves white silica on a surface of a substrate, after applied, to damage appearance. Therefore, the silica is needed to be removed with a tool such as a brush. When the composition is applied on a large area, costs to remove the silica is large.
Japanese Patent Application Laid-Open No. 2012-241100 describes a water absorption-preventing agent comprising an alkylalkoxysilane and a thixotropic agent. Generally, commercial thixotropic agents are dissolved in an organic solvent such as xylene, mineral spirit, i.e. mineral turpentine, benzyl alcohol, ethanol and isopropanol. That is, the water absorption-preventing agent comprising the thixotropic agent contains an organic solvent. A thixotropic agent containing no organic solvent is powder and, therefore, it is difficult to disperse the thixotropic agent in an alkylalkoxysilane.